A 120 megadalton plasmid harbored in Agrobacterium tumefaciens contains genetic determinants that confer on this organism properties tumorigenic to higher plant cells. Efforts are being made to identify and isolate these genes and their genetic products. Various genetic markers on this plasmid are being sought. The molecular events during the early phases of tumorigenesis are being studied with respect to the role of the plasmid in this abnormal process. BIBLIOGRAPHIC REFERENCES: Gardner, J.M. and C.I. Kado. 1976. A high molecular weight deoxyribonucleic acid polymerase from crown gall tumor cells of periwinkle (Vinca rosea). Biochemistry 15:688-697. Kado, C.I., ad P.F. Lurquin. 1976. Studies on Agrobacterium tumefaciens. V. Fate of exogenously added bacterial DNA in Nicotiana tabacum. Physiological Plant Pathology 8:73-82.